Patent Literature 1 discloses an electronic device such as a mobile phone that transmits air conduction sound and bone conduction sound to the user. In addition, Patent Literature 1 states that the air conduction sound is sound transmitted to the user's auditory nerve when vibration of the air caused by vibration of an object passes through the external auditory meatus to the tympanic membrane, and the tympanic membrane vibrates. Patent Literature 1 further states that the bone conduction sound is sound transmitted to the user's auditory nerve through a part of the user's body (e.g. the cartilage of external ear) being is in contact with a vibrating object.
In the telephone described in Patent Literature 1, a rectangular plate-like vibrator made of piezoelectric bimorph and flexible substance is attached to the outer surface of a housing through an elastic member. Patent Literature 1 also states that, when a voltage is applied to the piezoelectric bimorph of the vibrator, the piezoelectric material expands and contracts in a longitudinal direction, which causes the vibrator to bend and vibrate, and when the user brings his/her auricle into contact with the vibrator, air conduction sound and bone conduction sound are transmitted to the user.